Multimedia content delivery via Internet and other forms of network is creating more opportunities for content owners and content providers to reach a wider market. Specifically, the content providers publish their content on a network and users download the content based on the terms and conditions of the providers and use the same. Such network based electronic transactions help users get the kind of content they want when they want. Typical terms and conditions include electronic payment and granting of rights to use the content in a particular manner. Any violation of these granted rights by the users would result in (a) breach of contract and (b) potential loss of revenue for providers. It is one of the major requirements of the content industry to protect content and to ensure that there is a less and less of rights violations. Additional complexity arises due to the delivery of content to a multitude of devices (desktops, laptops, and handhelds), connected through a multitude of networks (wireline and wireless networks), and into a multitude of environments (homes, automobiles, and public places). While this broadens the reachability, at the same time, it increases the scope for granted rights violations. It is difficult to enforce rights if it can be violated easily. Availability of fairly easily accessible plain content is one of the reasons for violations and it is required to protect the content as much as possible while it is stored on a user device or while it being rendered.
Typically, content is protected by encrypting it at source and providing the key to decrypt the content whenever there is a need to use this content. While this process is quite adequate as a means for content protection, it is not without vulnerabilities. It depends on whether the decrypted content is available for manipulation. Specifically, the questions of interest are, is it possible to store the decrypted content, is it possible to access the decrypted content, or is it possible to send the decrypted content to another device? An affirmative answer to any of the above questions could potentially lead to rights violations. Any system that addresses any of these questions would help enforce content rights in an effective manner.